A new study shows men who got the least deep sleep were 80% more likely to develop high blood pressure than those who got the most.

Researchers determined how much deep sleep the men got by measuring the speed of their brain waves. People with poor-quality sleep spend a lot of time in "slow wave" sleep.

It's the first study to show that poor sleep quality independently raises the risk of high blood pressure, regardless of sleep duration or other sleep issues.

Previous studies have already linked sleep disorders such as obstructive sleep apnea and sleep-disordered breathing to an increased risk of high blood pressure.

Researchers say the results suggest the sleep quality is the third pillar of overall health. "People should recognize that sleep, diet and physical activity are critical to health, including heart health and optimal blood pressure control," says researcher Susan Redline, MD, in a news release.

Redline is a professor of sleep medicine at the Harvard School of Medicine. She says poor sleep may be a predictor of poor health.

The study is published in Hypertension: Journal of the American Heart Association.

The Sleep-Blood Pressure Connection

The study included 784 men ages 65 and over. Researchers looked at the relationship between several sleep characteristics and the risk of high blood pressure. The sleep characteristics included sleep duration, breathing patterns, and patterns of brain wave activity.

The men's blood pressure was measured and their sleep monitored at home at the start of the study and again about three and a half years later.

The men who spent less than 4% of their sleep in slow-wave sleep were much more likely to develop high blood pressure during the study.

Men with less slow-wave sleep were also more likely to have poor-quality sleep. Poor sleep included shorter sleep duration, more awakenings at night, and more severe sleep apnea.

Of all measures of sleep quality, researchers found slow-wave sleep was most strongly associated with the development of high blood pressure.

"Although women were not included in this study, it's quite likely that those who have lower levels of slow-wave sleep for any number of reasons may also have an increased risk of developing high blood pressure," says Redline.